Thank you for the suggestion! Unfortunately, his did not work for me: I installed version 1.5.12 correctly but the other Cryptomator version (or the remaining of it) kept existing in my Windows system (and this prevents me from installing the newest version of Cryptomator).
sorry, I forgot a step in my instruction. After installing version 1.5.12, you have to uninstall it with Revo Uninstaller. I used the pro version of RevoUninstaller, because it does a deeper check for leftovers. And after that, I reinstalled the actual version.